A power source is a device that converts other forms of energy into electrical energy. Power supply is divided into DC power supply and AC power supply. DC power has positive and negative pole. The positive pole has high potential and the negative pole has low potential. When the two poles are connected with the circuit, a constant potential difference can be maintained between the two ends of the circuit, so as to form a current from the positive pole to the negative pole in the external circuit. It converts other forms of energy into electrical power supply circuitries to maintain a steady flow of current.

 

In the circuit when talking about positive and negative, generally refers to the positive and negative of the power supply, and is the positive and negative of the direct current. DC power supply circuit, its power supply is generally divided into single power supply, including power supply and power supply ground; Dual power supply, including power supply and power supply negative. There are several ways to distinguish between positive and negative electrodes in a circuit.

 

 

Engineers in the design of PCB, will be the interface part of the pin definition with screen marking, for the positive and negative power supply, the general use of V+ and GND to distinguish the positive and negative power supply. Therefore, first look at the screen printing on the board, through the screen printing content on the board can learn a lot of information, the correct understanding of the screen printing information on the circuit board is very important.

 

 

Polar components are polar, in use can not be reversed. Commonly used polar components are electrolytic capacitors, diodes, etc. So the positive and negative poles of the circuit can be determined by the polar components. Take the electrolytic capacitor as an example, the positive electrode must be connected to the power supply, the negative electrode must be connected to GND, identify the pins of the capacitor can also determine the positive and negative of the circuit.

 

 

In the design of PCB, in order to improve the anti-interference ability and reduce the impedance of the ground wire, the ground will be copper clad in a large area to achieve electrical connection. If the circuit board is copper clad, it is basically based on GND as the network copper clad. It can be judged that the copper clad in a large area is the ground wire in turn.

 

 

Can also be identified by chip pins are negative, chips are need power supply, power supply pins, if you know the chip pins order can also distinguish between the power supply is negative, but this method has a defect, is only applicable for as long as a power network situation, if the circuit board with multiple power supply network, is still need further confirmation by above methods.